Micro-scale experimental investigation of deformation and damage of argillaceous rocks under hydric and mechanical loads

Argillaceous rocks are possible host rocks for underground nuclear waste repositories. Such rocks actually exhibit multi-scales heterogeneities, among which the scale of composite microstructure (clay matrix + mineral inclusions) is particularly interesting: the complex matrix-inclusion interaction under hydric and mechanical loadings is a potential source of damage. One important interest of this work is in the in-situ investigations at such a micro-scale, based on the combination of high resolution imaging by environmental scanning electron microscope and digital image correlation techniques. The results show complex localization patterns of deformation as well as some damage phenomena, both under purely hydric and combined mechanic/hydric loadings. Based on these observations, the deformation mechanisms can be identified, and the validation of standard poromechanics to describe the hydromechanical behavior of such rocks is discussed.